Bently Nevada 330425-01-00 Accelerometer Acceleration Transducer

The Bently Nevada 330425-01-00 is a high‑range piezoelectric accelerometer specifically configured for critical machinery monitoring applications where casing acceleration levels exceed the capabilities of standard 50 g sensors. This variant features the widely used ¼‑28 UNF integral mounting stud (suffix -01) and carries no hazardous area approvals (suffix -00), making it the ideal choice for non‑classified industrial environments that demand high‑amplitude vibration measurement capability without the regulatory overhead of explosion‑proof certifications.

The 330425 series is designed to meet American Petroleum Institute (API) Standard 670 for accelerometers, providing a 75 g peak amplitude range with a sensitivity of 25 mV/g. The 330425-01-00 is the higher‑range sibling of the 330400-01-00, sharing the same mechanical dimensions, rugged construction, and environmental sealing, but offering a lower sensitivity to accommodate larger vibration signals without saturation. It is particularly well‑suited for high‑speed gearboxes, reciprocating compressors, high‑energy turbines, and other machinery where vibration transients or steady‑state amplitudes routinely exceed 50 g.

This configuration combines the standard ¼‑28 UNF thread – prevalent in North American and many international installations – with the cost‑effective non‑certified option. It delivers the full performance of the 330425 platform: 75 g peak amplitude range, 25 mV/g sensitivity, 10 Hz to 15 kHz frequency response, and IP68‑rated hermetic sealing for harsh environments. Its case‑isolated design eliminates ground loops, and the integral stud ensures a secure, low‑loss mechanical coupling.

This introduction focuses exclusively on the 330425-01-00 configuration, highlighting its unique high‑amplitude capabilities, comparing it with lower‑range alternatives (such as the 330400-01-00) and with other 330425 variants (different threads and certifications), to guide proper selection for demanding non‑hazardous area applications.

Functional Description and High‑Amplitude Design Philosophy

The 330425-01-00 accelerometer operates on the piezoelectric principle, converting mechanical acceleration into an electrical charge that is conditioned into a low‑impedance voltage signal. Its sensitivity of 25 mV/g (2.5 mV/m/s²) is intentionally lower than the 330400’s 100 mV/g to extend the usable measurement range to 75 g peak without saturating the amplifier. This design trade‑off is essential for machinery with inherently high vibration levels, where a 50 g sensor would clip the signal, resulting in inaccurate amplitude readings and potentially missed fault indications.

The 75 g range provides a 50% margin over the 330400, accommodating transient spikes, start‑up resonance crossings, and steady‑state high‑amplitude vibrations common in certain rotating equipment. The amplitude linearity of ±1% up to 75 g ensures that the output remains proportional to the input across the entire operating range, enabling reliable trend analysis and alarm thresholds.

The frequency response of the 330425-01-00 is identical to the 330400: 10 Hz to 15 kHz (±3 dB) and 30 Hz to 10 kHz (±10%). This broad bandwidth covers most machinery vibration components, including gear mesh frequencies (often >1 kHz), blade pass frequencies, and bearing defect signatures. The lower sensitivity does result in a proportionally higher noise floor compared to the 330400, but for high‑amplitude applications, the signal‑to‑noise ratio remains acceptable. The datasheet does not specify a noise floor for the 330425, but it is typically scaled from the 330400’s 0.004 g rms.

The 330425-01-00 is mechanically identical to the 330400-01-00: 23 mm diameter, 59 mm height (including stud), 99 g weight, and 3‑pin MIL‑C‑5015 connector. It uses the same mounting torque (4.1 N·m) and the same cable options (130539, 169253, 167103). This mechanical interchangeability allows users to upgrade from a 330400 to a 330425 without changing mounting hardware or cabling, provided the vibration levels justify the change.

Detailed Comparison with Bently Nevada 330400-01-00 – When to Choose 330425?

To assist in proper sensor selection, the following table compares the 330425-01-00 with its lower‑range counterpart, the 330400-01-00, as well as with other 330425 configurations (different threads and certifications). This highlights the unique value of the -01-00 for high‑amplitude, non‑hazardous applications.

Selection Guide – Key Differences

The 330425-01-00 is the standard ¼‑28 UNF, non‑certified, high‑range accelerometer. It is the direct high‑amplitude equivalent of the 330400-01-00. Choose this variant when:

• Peak vibration amplitudes routinely exceed 50 g.

• The machinery is in a non‑hazardous (safe) area.

• The mounting thread is ¼‑28 UNF.

• You do not require explosion‑proof or intrinsic safety certifications.

If you need metric thread (M8), choose 330425-02-00 (custom order). If you need hazardous area approvals, choose 330425-01-05. If your vibration levels are consistently below 50 g, the 330400-01-00 offers higher sensitivity (100 mV/g) for better low‑amplitude detection.

Hardware Characteristics – Specific to 330425-01-00

Physical Dimensions and Mounting

• Thread: ¼‑28 UNF integral stud (male). This standard thread is compatible with many mounting bases, adapters, and existing installations in North America and worldwide.

• Height: 59 mm (2.3 in) including stud.

• Diameter: 23 mm (0.93 in).

• Weight: 99 g (3.5 oz) typical (no cable).

• Mounting Surface Finish: Recommended 32 µin rms or better.

• Mounting Torque: 4.1 N·m (3.0 ft·lb). Over‑tightening can damage the stud or housing.

Connector and Cabling

• Connector: 3‑pin MIL‑C‑5015 receptacle (316L stainless steel). This is the industry‑standard connector for these accelerometers.

• Compatible Cables:

  • 130539: 18 AWG, 3‑conductor shielded, with fluorosilicone boot.

  • 169253: 22 AWG, 3‑conductor shielded.

  • 167103: 22 AWG, armored.

• Maximum Cable Length: 305 metres (1000 ft) without signal degradation.

• Mating Connector: 00531080 (for custom cable assembly).

Environmental and Electrical Specifications

• Power: -24 V dc ±0.5 V, 2 mA nominal bias current.

• Output Bias Voltage: -8.5 V dc ±0.5 V.

• Grounding: Case isolated – essential for avoiding ground loops.

• Operating/Storage Temperature: -55°C to +121°C (-67°F to +250°F).

• Shock Survivability: 5000 g peak.

• Humidity: 100% condensing (hermetically sealed case).

• IP Rating: IP68 (sensor only) – dust tight and watertight.

• Magnetic Field Susceptibility: < 225 mg/gauss at 50 gauss, 50‑60 Hz.

Base Strain Sensitivity Notes

Base strain sensitivity can affect low‑frequency measurements if the mounting surface flexes. For the 330425-01-00:

• If the serial number begins with “G” (newer sensors): Base strain sensitivity is only 0.005 g/mstrain – no extra mounting base required.

• If the serial number does NOT begin with “G” (older, pre‑April 2004): Base strain sensitivity is 0.100 g/mstrain without the mounting base, but reduces to 0.0005 g/mstrain when using the supplied Mounting Base (API adapter) – part number 37439-01 (¼‑28 to ¼‑28). Bently Nevada recommends using the base for these older units.

Application Guidelines – When to Use 330425-01-00

The 330425-01-00 is recommended for machinery where peak vibration levels commonly exceed 50 g. Typical applications include:

• High‑Speed Gearboxes – Gear mesh forces can produce high‑amplitude, high‑frequency vibrations that may saturate a 50 g sensor. The 75 g range provides ample headroom.

• Reciprocating Compressors – Impact forces from piston motion and valve operation generate high g‑levels; the 75 g range ensures accurate capture of these transients.

• Turbine Blade Pass Frequencies – In certain turbine stages, blade pass vibrations can be high in amplitude, especially under off‑design conditions.

• Heavy‑Duty Industrial Fans and Blowers – Large imbalance or aerodynamic forces can produce high casing accelerations.

• Testing and Commissioning – When vibration levels are unknown or expected to be high, the 330425 offers a safer margin.

When to choose 330400-01-00 instead:

• Expected peak vibration levels are consistently below 50 g.

• Higher sensitivity (100 mV/g) is needed to detect low‑amplitude bearing defects or early‑stage faults.

• You prioritize signal‑to‑noise ratio over range extension.

Installation Best Practices for 330425-01-00

To achieve accurate, repeatable measurements with the 330425-01-00:

1. Surface Preparation – Clean the mounting surface to remove paint, rust, or debris. Achieve a surface finish of 32 µin rms or better (e.g., by lapping). This ensures proper mechanical coupling and frequency response.

2. Stud Installation – Apply a thin layer of anti‑seize compound (if required) and hand‑tighten the integral stud into the prepared hole. Then torque to 4.1 N·m (3.0 ft·lb). Do not use the connector housing to apply torque; use a wrench on the hex flats of the stud.

3. Cable Connection – Align the 3‑pin connector and tighten the coupling nut securely. For long cable runs, use the recommended 18 AWG cable (130539) to minimise voltage drop and signal loss. Route cables away from high‑voltage lines and avoid sharp bends.

4. Grounding – Because the case is isolated, the sensor does not require a separate ground. However, the cable shield should be connected to the monitoring system’s common reference at the power supply end to minimize electrical noise.

5. Base Strain Consideration – If the sensor’s serial number does not begin with “G”, install the supplied Mounting Base (37439-01 for ¼‑28) between the stud and the machine surface. This reduces base strain sensitivity dramatically.

6. Environmental Protection – For outdoor installations, use splash boots (available separately) and ensure all cable connections are sealed. The sensor itself is IP68, but the cable termination may require additional protection.

Comparison with Other High‑Range Options – Why Choose 330425-01-00?

• vs. 330400-01-00 – The 330425-01-00 offers 75 g range (vs. 50 g) but lower sensitivity (25 mV/g vs. 100 mV/g). Choose the 330425 when vibration levels exceed 50 g; choose the 330400 for better low‑amplitude detection.

• vs. 330425-02-00 – Both are non‑certified and have identical performance. The -02 uses M8 x 1 thread; the -01 uses ¼‑28 UNF. Choose based on your machinery’s mounting standard.

• vs. 330425-01-05 – The -05 adds hazardous area approvals (ATEX, IECEx, CSA). If your installation is in a safe area, the -00 is more economical and does not require certified barriers.

Ordering Information

When ordering the 330425-01-00, use the full part number exactly as shown:

• 330425 – Base model (accelerometer, 75 g, 25 mV/g)

• -01 – Mounting thread: ¼‑28 UNF integral stud

• -00 – Agency approval: None

Compatible Cables and Accessories

Note: The 330425-01-00 does not include a cable; order separately. Ensure cable length does not exceed 305 m.

Certifications and Compliance

Because the -00 option has no hazardous area approvals, it is certified for general industrial use only. It complies with:

• FCC Part 15 – Radio frequency interference limits.

• EMC Directive 2014/30/EU – Electromagnetic compatibility.

• RoHS Directive 2011/65/EU – Restriction of hazardous substances.

• China RoHS – EFUP of 15 years (SJ/T 11364-2024).

• ABS – (Marine Vessels, Offshore Units) – the sensor itself is approved for maritime use even without explosion protection.

It is NOT rated for ATEX, IECEx, or CSA hazardous locations. If your installation requires intrinsic safety, you must order the -05 option (e.g., 330425-01-05).

Warranty and Support

The Bently Nevada 330425-01-00 is covered under the standard manufacturer’s warranty (refer to Bently Nevada Terms and Conditions). For technical support, application assistance, or custom configurations, contact your local Bently Nevada sales representative or access the Bently Nevada Media Library at bntechsupport.com.